1. Field of the Invention
The invention pertains to a nozzle, namely a part that is designed to be placed in a hydraulic or pneumatic system and having a hole calibrated to limit or regulate the delivery of the fluid flowing in the system. It also pertains to a device for the application of a nozzle of this type.
2. Description of the Prior Art
There are nozzles in the fuel-injection devices of engines or in jacks or valves or else, again, in certain devices for dampening the vibrations to which any elements or systems may be subjected, or which may be produced by these elements or systems.
However, the nozzles used in these various applications have the disadvantage of having a delivery rate which is proportionate to the square root of the pressure differential existing between the inlet and the outlet of the calibrated hole. More precisely, the delivery rate is proportionate to the product of the square root of the pressure differential by the area of the hole. This particular feature may be troublesome in certain cases, especially when it is sought to obtain a specific delivery rate at the outlet of the nozzle by using it in a loop for the regulation of the delivery rate. For, in this precise instance, if it is sought to double the delivery rate with respect to a given value, the pressure differential corresponding to the value must be multiplied by 4. This means, for example, that if the outlet hole of the nozzle is in a zone having a constant pressure, the inlet pressure must be made to vary in order to cause a variation in the delivery rate. It also means that if the outlet pressure is small compared to the inlet pressure, it is necessary to multiply the inlet pressure practically by a factor of 4 to double the outlet delivery rate.
In a case of this type, the pressure needed at the inlet of the injector varies almost exponentially, and when the values become high, great variations are necessary in the inlet pressure to obtain appreciable variations in the delivery rate. Now the inlet pressure is given by means placed upstream of the hydraulic or pneumatic circuit, and the result of this is that the energy needed to actuate these means also varies almost exponentially. Since the efficiency of the said means is not perfect and is not constant along its entire range of use, the relative difference between the energy given to these means and the energy that they produce is all the greater as the delivery rate and/or input power values diverge from the rated value which can be given by the said means.
The nozzle of the invention does not have these disadvantages.
According to the invention, a nozzle comprises means so that the dimensions of the hole for the flow of fluid vary according to the pressure differential existing between its inlet and its outlet.
According to another characteristic of the invention, the nozzle has a flat part through which at least two cuts are made, defining at least one tongue designed to be placed in the path of the fluid and capable of being deflected elastically when there is a pressure differential between its two sides.
According to another characteristic of the invention, when there is no pressure differential on either side of the tongue, its main plane and the plane of the flat part on which it is made are identical and, when there is a pressure differential, the tongue is deflected towards the zone where there is low pressure.
Consequently, when the tongue or tongues are in the idle position, the hole for the flow of fluid is at its minimum size. The area of the said hole then corresponds to the total area of the cuts made in the flat part. When the pressure differential increases, the tongue or tongues are deflected and the cross-section of the fluid passage also increases. The delivery rate is therefore greater than the delivery rate that would have been had if the cross-section had not undergone variation.
In one embodiment of the nozzle, the cuts are made in such a way that at least one part of the delivery rate curve as a function of the differential pressure is linear, the delivery rate in this part being directly proportionate to the differential pressure between the inlet and the outlet.